The present invention relates to the art of docks and related structures which are used to store and transfer goods and equipment, especially cargoes, between the land and a vessel in the water.
Waterfront land is expensive, usually because it is unavailable in sufficient quantity where needed. Where land is available there are often competing "higher and better uses". Some ports must resort to filling portions of the bodies of adjacent water to create land. These alternatives are pursued at great expense and environmental impact.
Many necessary waterfront activities are inherently land intensive. In cargo handling activities, shipping containers are often parked on paved land surfaces while still mounted on a highway worthy chassis. Such container storage areas must also include vehicle circulation areas for maneuvering the units around the parking spaces and for moving them between the parking spaces and the dock. At the dock the containers are transferred to or from a vessel. Similarly, bulk cargoes such as coal and wood chips are often stored in stacks on the land surfaces behind the dock. These stacks expand horizontally with the addition of more materials, occupying disproportionately large areas of land for the volume of material stored. Other dry bulk, liquid bulk, and break bulk cargoes are stored in warehouses or tank farms behind the docks. These warehouses and tanks not only occupy significant backlands, they are also expensive to build and maintain. In urban areas even non-cargo operations such as hotels, sports complexes, etc., generate the need for parking and warehousing operations that occupy large waterfront land areas. The present dock invention is intended to consolidate and intensify these types of activities inside, on and near the dock, thereby reducing the need for waterfront land to be used as storage areas.
Some warehousing and storage facilities on the waterfront include the means for refrigerating their cargo contents. This capability is provided at a high initial cost of refrigeration equipment and insulation materials. It also entails high operational and maintenance costs, especially in warmer climates. The present dock invention is intended to incorporate the means to greatly mitigate these initial and ongoing costs of conventional refrigerated storage, harnessing the predictably lower temperature of the body of water adjacent to many dock locations in the refrigerating effort. The storage strategy of the present dock invention also takes advantage of the fundamental tendency of warmer air to rise and cooler air to fall.
When the congestion of competing activities near the waterfront force land intensive activities to expand away from the water's edge, farther into the backlands, increased operational expenses are incurred. Shipping containers stored away from the waterfront must be drayed between storage and the dock for a vessel loading or unloading operation. Sometimes this drayage must include the use of public thoroughfares, thus making an already troublesome urban traffic problem even worse. When bulk cargo materials are stored away from the water's edge, expensive conveyors are often installed to facilitate the transfer of these cargoes between storage and the vessel during loading and unloading operations. The maintenance and cleaning of these conveying systems is troublesome and expensive. Moreover, different bulk materials have different handling characteristics and their conveying systems must sometimes be optimized for a few types of materials at the expense of efficient handling of others. This multiplicity of cargo characteristics, the related infrastructure and equipment needs and the cargo handling techniques for each cargo type are all reasons why it is difficult to use a single dock for several cargo types, either at the same time or in sequence. The present dock invention is intended to simplify the operational implications of moving a wide variety of cargoes between storage and the vessel by creating significantly more storage at the waterfront than is currently available. It will also eliminate the need for much of the equipment and labor traditionally employed in the transfer between storage and the vessel, thereby eliminating many of the traditional conflicts inherent in handling a variety of cargoes at a single dock. Similarly, this invention is intended to consolidate other non-cargo parking and warehousing functions on the waterfront.
Even where conventional storage facilities are already conveniently located near the dock, the actual transfer between storage and the vessel is often a frenzied operation which involves intense concentrations of labor and equipment. The present dock invention is intended to improve this transfer operation by eliminating some of the presently necessary activities along with their related labor and equipment.
Oftentimes, cargo storage facilities on the waterfront are either inadequate or inefficient and cause awkward and expensive vessel loading and unloading operations. This is inherent in some dry bulk operations which perform indirect cargo transfers between a train and a vessel to obviate the need for waterfront storage facilities. In a typical instance the arrival of a mile long "unit train" is synchronized with the arrival of a large bulk carrier vessel. The bulk product is then dumped from the train into a pit, reclaimed to a conveyor, conveyed to the dock, and piped through a loading arm, into the vessel hold. Such an operation, and the cleanup in its aftermath, is labor and equipment intensive. Further, sometimes the movements of the vessel and the train cannot be adequately coordinated and large unintended demurrage costs are encountered by one or both. The present dock invention is intended to weaken or sever the link between the arrival of the train and the arrival of the vessel and, at the same time, reduce the labor and equipment intensity needed for this type of cargo transfer operation.
As shown in FIG. 1, most modern docks (e.g., dock 100) incorporate a rigid horizontal platform 102, usually supported by piles 104, across which cargoes can be efficiently transferred between land and vessel. This platform is usually designed to support its own weight, the weight of a modest amount of staged cargo and the weight of the vehicles and handling equipment needed to effect the cargo transfer to and from the vessel. Such a dock system usually also includes a means for stabilizing the earth at the water's edge. As illustrated in FIG. 2, the earth's slope behind the dock is often comparatively unstable in its normal state and would be made more unstable if cargo and equipment loads 202 were to be superimposed on its surface. There would be a strong tendency for the earth to undergo the classic, possibly catastrophic, slip failure (represented by slip circle 204) under these superimposed loads. Such an earth failure could cause massive amounts of earth to slide into the water carrying the dock and related cargo and equipment with it (reminiscent of the classic landslide on shore). Consequently, the earth's slope stability at the water's edge must often be enhanced by installing a retaining wall structure 106. Sometimes the earth pressures behind this retaining wall are mitigated by installing a pile supported relieving platform 108 to carry some of the weight of the earth and the superimposed loads down deeper into the soils. At other times the pile supported platform is built wider over a long and gradual slope of the bank, which has been armor protected with rock to retain its stability. All of these structural techniques come at high cost for the utility of transferring cargoes between the land and the vessel. The present invention is intended to provide both the rigid transfer platform and the means of enhancing the earth's stability in a different form that also provides the storage consolidation and cargo handling improvements promised above.
Modern docks are also constructed using caissons. These caissons are concrete boxes which are fabricated hollow so that they can be floated into position. When positioned, they are ballasted until they sink and come to rest on a previously prepared bottom. Subsequently, the boxes are filled to the top with ballast such as rock and a top lid of concrete is poured to form the rigid cargo transfer platform of a dock. These filled concrete boxes then serve as a gravity dam or gravity retaining wall as land is filled in behind them to create the smooth transition to the shore which is needed for cargo handling. The land fill is usually paved for cargo loads. In this approach to dock construction, the concrete boxes (caissons) replace both the rigid pile supported cargo transfer platform and the earth slope stability enhancements of the more conventional dock approach.
Floating docks have also been used as rigid cargo transfer platforms, both with and without accompanying earth stability enhancing structures. These floating docks resemble a barge or pontoon assembly and they employ only the water's buoyant forces to support the dock, cargo and equipment loads where more conventional dock designs transfer these loads to the soils below. The present dock invention massively increases the cargo stored on and in the dock, proportionally increasing the total loads of the dock and its contents. Its design harnesses very large buoyant forces (well beyond those previously employed in the floating dock design art) and, at the same time, it employs soil bearing pressures and earth anchors to carry the significantly increased earth, dock, cargo and equipment loads.
One of the greatest advantages of a traditional floating dock concept is the ability to fabricate the dock at a preferred location, remote from the location of intended use, and then tow the nearly complete assembly into place using conventional maritime transportation techniques. In fact, one can conceive of actually relocating a floating dock from an initial working location to another working location if the needs change. In the context of military operations, the ability to relocate a dock structure to the forward areas of a contingency operation creates powerful logistics advantages. During World War II, the American forces employed a "DeLong Pier" to great advantage. This was a steel barge/pontoon which was floated and towed across the water into the remote place of need. The barge was then jacked into the air on spud piles which were threaded through spud wells fabricated into the deck of the barge. The jacked up barge then became a rigid cargo transfer platform resembling a conventional dock and the spud piles transferred all loads into the soils below. The present dock invention extends, expands and alters the concept embodied in the DeLong Pier. The present dock can be fabricated off site, ballasted to stability and towed to a site for final installation. Unlike the DeLong and other traditional floating docks, the present dock invention is then further ballasted to lower (instead of raise) it into its final position where it is then anchored to the soil sufficiently to mechanically overcome the net positive buoyant force that will be present when the cells are emptied of ballast and made ready to receive cargoes for storage. The present dock invention is then emptied of ballast and the hollow cells are used for cargo storage. Later, the dock cells can be reballasted to overcome net positive buoyant forces, disconnected from their earth anchorage, reballasted for towing stability and then towed to a new location installation. The reballasting for towing stability during transport can include the loading of actual cargoes to facilitate a military operations in the forward areas. Thus, the present dock invention can serve as a cargo carrier when it is in transit. It will then serve as a highly efficient dock when installed at the battlefront and all of its initial cargo has been off loaded.
In many cases existing conventional docks are reaching the end of their useful life span for one or more reasons which will be discussed with reference to FIG. 3. One common reason for the diminishing utility of a conventional dock is that it was not designed for the dredge depth that is currently needed by modern ships. Another is that it was not designed for gantry or other crane loads that are currently needed by modern cargo handling techniques. Yet another is that such a dock has insufficient apron width 302 for modern cargo handling operations. In addition, such a dock might incorporate a sheetpile wall earth retaining structure 304 or an armor coated bank slope 306 which is progressively failing and is prohibitively expensive to repair or replace. Finally, such a dock may have insufficient cargo storage capacity in the backlands and no additional land is available. The present dock invention concept is intended to be applied to the rehabilitation of existing conventional docks to solve any or all of the deficiencies listed above and to prolong their remaining useful life. Further, after the present dock invention concepts have been applied to prolong the life of a distressed existing conventional dock, it will then be possible to convert the distressed dock into a thoroughly new dock with a minimum of additional cost once the old parts of the structure are no longer serviceable.